Java对象clone()的测试

Object中自带native clone()方法.

研究了一下用法.

  1 public class DeepCopyTest {
  2 
  3     public static void main(String[] args) throws CloneNotSupportedException {
  4 
  5         test1();
  6         System.out.println("-----------------------------");
  7         test2();
  8 
  9     }
 10 
 11     static void test1() throws CloneNotSupportedException {
 12         Teacher t1 = new Teacher();
 13         t1.settName("LaoLi");
 14 
 15         Teacher t2 = new Teacher();
 16         t2.settName("LaoWang");
 17 
 18         Stu stu = new Stu();
 19         stu.setName("name_1");
 20         stu.setAge(23);
 21         stu.setScore(129);
 22         stu.setTeacher(t1);
 23 
 24         Stu stuCopy = stu.clone();
 25         System.out.println("1:" + stu.toString());
 26         System.out.println("2:" + stuCopy.toString());
 27 
 28         stuCopy.setName("name_2");
 29         stuCopy.setAge(25);
 30         stuCopy.setScore(133);
 31         stuCopy.setTeacher(t2);
 32 
 33 
 34         System.out.println("11:" + stu.toString());
 35         System.out.println("22:" + stuCopy.toString());
 36 
 37     }
 38 
 39     static void test2() throws CloneNotSupportedException {
 40         Teacher t1 = new Teacher();
 41         t1.settName("LaoLi");
 42 
 43         Teacher t2 = new Teacher();
 44         t2.settName("LaoWang");
 45 
 46         Stu stu = new Stu();
 47         stu.setName("name_1");
 48         stu.setAge(23);
 49         stu.setScore(129);
 50         stu.setTeacher(t1);
 51 
 52         Stu stuCopy = stu.clone();
 53         System.out.println("1:" + stu.toString());
 54         System.out.println("2:" + stuCopy.toString());
 55 
 56         stuCopy.setName("name_2");
 57         stuCopy.setAge(25);
 58         stuCopy.setScore(133);
 59         stuCopy.getTeacher().settName("LaoKong");
 60 
 61 
 62         System.out.println("11:" + stu.toString());
 63         System.out.println("22:" + stuCopy.toString());
 64 
 65     }
 66 
 67 }
 68 
 69 class Teacher {
 70     private String tName;
 71 
 72     public String gettName() {
 73         return tName;
 74     }
 75 
 76     public void settName(String tName) {
 77         this.tName = tName;
 78     }
 79 
 80     @Override
 81     public String toString() {
 82         return ToStringBuilder.reflectionToString(this, ToStringStyle.SHORT_PREFIX_STYLE);
 83     }
 84 }
 85 
 86 class Stu implements Cloneable {
 87     private String name;
 88     private int age;
 89     private Integer score;
 90     private Teacher teacher;
 91 
 92     public Teacher getTeacher() {
 93         return teacher;
 94     }
 95 
 96     public void setTeacher(Teacher teacher) {
 97         this.teacher = teacher;
 98     }
 99 
100     public String getName() {
101         return name;
102     }
103 
104     public void setName(String name) {
105         this.name = name;
106     }
107 
108     public int getAge() {
109         return age;
110     }
111 
112     public void setAge(int age) {
113         this.age = age;
114     }
115 
116     public Integer getScore() {
117         return score;
118     }
119 
120     public void setScore(Integer score) {
121         this.score = score;
122     }
123 
124     public Stu clone() throws CloneNotSupportedException {
125         return (Stu) super.clone();
126     }
127 
128     @Override
129     public String toString() {
130         return ToStringBuilder.reflectionToString(this, ToStringStyle.SHORT_PREFIX_STYLE);
131     }
132 
133 }
View Code

 

执行结果:

1:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
2:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
11:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
22:Stu[name=name_2,age=25,score=133,teacher=Teacher[tName=LaoWang]]
-----------------------------
1:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
2:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
11:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoKong]]
22:Stu[name=name_2,age=25,score=133,teacher=Teacher[tName=LaoKong]]

 

基本验证了这样的结论:

基本类型,不变类型可以做到值拷贝效果.不变类型其实是引用发生了变化.

对象类型,实际上是引用拷贝.

设置一个新对象,stuCopy.getTeacher().setName("LaoKong")

引用其实发生了变化.-->指针A指向空间KK, 指针B也指向空间KK, 指针指向的地址KK中的内容替换掉.

 

而把对象重新设值, stuCopy.setTeacher(t2)

其实是把对象引用的地址指向新的对象. -->指针A指向空间KK, 指针B也指向空间KK, 指针BB指向新的空间KKK.

 

----------------------------------------------------

/* 浅复制 */  
public Object clone() throws CloneNotSupportedException {  
    Prototype proto = (Prototype) super.clone();  
    return proto;  
}  

/* 深复制 */  
public Object deepClone() throws IOException, ClassNotFoundException {  

    /* 写入当前对象的二进制流 */  
    ByteArrayOutputStream bos = new ByteArrayOutputStream();  
    ObjectOutputStream oos = new ObjectOutputStream(bos);  
    oos.writeObject(this);  

    /* 读出二进制流产生的新对象 */  
    ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());  
    ObjectInputStream ois = new ObjectInputStream(bis);  
    return ois.readObject();  
}

 

posted @ 2018-12-27 20:08  multitude  阅读(313)  评论(0)    收藏  举报